<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title>签名案例</title>
	</head>
	<body>
		<canvas id="canvas" width="1000" height="1000" style="border:2px dashed red;"></canvas>
		<button id="button">清除案例</button>
		<script>
			window.onload = function() {
				var canvas=document.getElementById("canvas");
				var cxt=canvas.getContext("2d");
				
				
				var canvasx=canvas.getBoundingClientRect().left;
				var canvasy=canvas.getBoundingClientRect().top;
				console.log(canvasx);
				console.log(canvasy);
				canvas.addEventListener("mousedown",downfun);
				canvas.addEventListener("mousemove",movefun);
				canvas.addEventListener("mouseup",upfun);
				
				
				var startx;
				var starty;
				var endx;
				var endy;
				cxt.lineWidth=3;
				var offon=false;
				
				
				
				function downfun(e){
					offon=true;
					startx=e.clientX-canvasx;
					starty=e.clientY-canvasy;
				}
				function movefun(e){
					if(offon==true){
					cxt.beginPath()
					endx=e.clientX-canvasx;
					endy=e.clientY-canvasy;
					cxt.moveTo(startx,starty);
					cxt.lineTo(endx,endy);
					cxt.stroke();
					
					startx=endx;
					starty=endy;
					console.log("1111")
					}
				}
				function upfun(){
					offon=false;
					cxt.closePath();
				}
				document.getElementById("button").onclick=function(){
					cxt.clearRect(0,0,canvas.width,canvas.height);
				}
				
			}
		</script>
	</body>
</html>
